Mechanical devices for inserting pins one at a time into cooperating holes in work pieces are now in use in industry. Two such mechanisms are shown in U.S. Pat. Nos. 3,788,537 and 3,982,679. In the use of these devices, it is essential that the work piece and the pin driving means be precisely spaced so that the pin when inserted in the work piece will enter to the exact required depth. Where there are long runs in which one sized pin is inserted into work pieces of uniform vertical dimensions, the need for quick set up time is not present. On the other hand, where there are short runs with the pin receiving pieces being of varying vertical dimensions, the set up time assumes substantial importance in the cost of the operation.